A process for the catalytic oxidation of HCl gas is described in European Patent No. EP 233 773 B1, in which a HCl gas contaminated with organic impurities such as benzene, chlorobenzene and the like is prepurified for use in a Deacon process (catalytic HCl oxidation by means of oxygen). In the prepurification described therein, activated carbon is used as the adsorber and is regenerated after use. It is further proposed to regenerate the adsorber at elevated temperatures or under reduced pressure and optionally using an inert gas.
One disadvantage of such a process is that the production process and the HCl purification process must be interrupted for regeneration of the activated carbon bed. A further disadvantage of such a process is that the regeneration is conducted thermally or at reduced pressure, which is disadvantageous in terms of energy, or is carried out using an inert gas, which is expensive.
Adsorptive separation to remove contaminants from gas streams, particularly organic contaminants, is frequently used in chemical processing.
As adsorbents are used, they periodically require regeneration. During regeneration of an adsorbent, the adsorbent is conventionally heated and brought into contact with a regenerating gas stream. The adsorbed components thereby dissolve in the regenerating gas stream and the adsorbent is unloaded.
The achievable pity of the gas stream from which the contaminants are to be removed can depend greatly on the regeneration of the loaded adsorbent.
Conventional regeneration processes generally use heated inert gas or steam in order to introduce the required heat energy and the required regenerating gas stream into the system simultaneously. Steam can only be used in cases where moisture can be tolerated within the process. In the case of the working up of crude hydrogen chloride gas, attempts are made to avoid introducing water in order to prevent corrosion of apparatus that comes into contact with the product.
When inert gases (e.g. nitrogen, etc.) are used in regeneration, however, the amounts of gas that must be used to provide a continuous stream of fresh regenerative gas give rise to high costs. If, on the other hand, a circulatory regeneration system with inert gases is used, then components dissolved in the inert gases during regeneration of the adsorber must be depleted before recycling the inert gases to the circulatory system. Otherwise, the regeneration achieved would not be sufficient to provide the required process gas purities during the adsorption operation.